Question SSD and GC

USAFRet

Titan
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Mar 16, 2013
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From what I have read trim is just an aid for GC.
If true and GC never runs then trim won't help.
That GC only runs if TRIM does not.
"The purpose of this feature is to maintain the SSD's performance in environments where Trim (discussed here) is not functioning normally."

And then, only if there is no idle time.
 


Just uBlockOrigin
I also use UBO but just with the default blockers and don't see that but that's a different issue.

Here's a piece of the article.
It seems to say that trim is just an aid for GC.

Garbage collection with the TRIM command


Garbage collection manages and maintains the available storage space, handling the disparity between the erase unit size (block) and the read/write unit size (page). When a previously written block is targeted for garbage collection, the valid data pages are gathered up and moved to another block on the SSD so that the block containing the old, invalid data pages can be erased. Garbage collection may wait for lulls in drive activity to initiate the process, sometimes leaving pages that are obsolete in the SSD.

SSD TRIM is complementary to garbage collection. The TRIM command enables the operating system (OS) to preemptively notify the SSD which data pages in a particular block can be erased, allowing the SSD's controller to more efficiently manage the storage space available for data. TRIM eliminates any unnecessary copying of discarded or invalid data pages during the garbage collection process to save time and improve SSD performance.

The SSD TRIM command simply marks the invalid data and tells the SSD to ignore it during the garbage collection process. The SSD then has fewer pages to move during garbage collection, which reduces the total number of program/erase cycles (P/E cycles) to the NAND flash media and prolongs the life of the SSD. NAND flash wears out due to the long-term effects of the P/E cycle, so reducing the number of erases can lengthen the endurance of the SSD.

In order for TRIM to function, the host's OS and the SSD must support it. For example, in a Windows environment, when an SSD reports that it has TRIM support, the OS will disable disk defragmentation and enable TRIM. When a user deletes a file, the OS sends a TRIM command to the SSD controller to tell it which data pages can be erased when the garbage collection process takes places. The TRIM command and the write command operate independently of each other. The user also has the option to initiate the TRIM command manually or schedule it on a daily basis.





 

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